Jens Standfuss

Laser beam welding of atmosphere aluminum die cast material using high frequency beam oscillation and brilliant beam sources

In the serial production of components for automotive applications such as cooling and air-conditioning systems, aluminum die-cast materials are frequently used due to their excellent castability. The aim of providing light weight components can be approached with thin walled cross sections even for complex structural parts. However, cast components are usually connected to semifinished products such as profiles or tubes. The connections have to be mostly pressure tight. The joining technique for these applications has to be highly productive to obtain high component outcome and cost-efficient. Laser beam welding techniques are especially suitable for these tasks. Die-cast components have limited or no weldability due to their manufacturing process. This is due to entrapped gases within pores or cavities under high pressure conditions. Furthermore, the mold release agents for the die-cast process are inappropriate for obtaining homogeneous and sound weld seams. Consequently, this results in a larger numbe...

Laser-multi-pass-welding of aluminiun and steel with sheet thickness above 50 mm

Thick-walled components made of steel or aluminum alloys are widely used for industrial applications.Welded steel components with sheet thicknesses of 50 mm and above are used for example in big mobile cranes, housings of turbines for power plants and for the base plate of servo-hydraulic presses for automotive body parts etc.Thick-walled welded aluminum components can be found in applications of the chemicals industry and for transportation of liquid natural gases such as LNG tanker.For both material types conventional arc welding technologies are state of the art, often manually performed. Caused by size of the welding torch and the limited penetration depth of multi-pass welding, grove angles of 45° or more are essential. This leads to a high volume weld metal and a high heat input into the base material as well as to a high consumption of filler material. Weld distortion and therefore straightening of the components are cost drivers, too.The paper will be present the latest developments at the Fraunhofer IWS for laser-multi-pass-welding (laser-MPNG) using brilliant solid state laser with laser power of approximately 3 kW for welding aluminum as well as high power diode laser with up to 10 kW for welding of steel.Brilliant laser sources (fiber, disk) with a beam parameter product of 0.4 mm mrad and laser power up to 3 kW are used for multi-pass-narrow-gap welding of aluminum for welding depth of 50 mm and above. Very low groove angles of less than 4° are used, which leads to seam width of max. 4 mm@50 mm welding depth. Using high power diode laser with laser power of up to 10kW the groove angle can be reduced to 12° by using an edge preparation by plasma cutting as known from conventional arc welding technologies.Summarized potential industrial application will be presented. A comparison of laser-multi-pass-narrow-gap welding with the state of the art conventional welding technologies will be given with respect to welding speed, energy input per unit length as well as filler material consumption.Thick-walled components made of steel or aluminum alloys are widely used for industrial applications.Welded steel components with sheet thicknesses of 50 mm and above are used for example in big mobile cranes, housings of turbines for power plants and for the base plate of servo-hydraulic presses for automotive body parts etc.Thick-walled welded aluminum components can be found in applications of the chemicals industry and for transportation of liquid natural gases such as LNG tanker.For both material types conventional arc welding technologies are state of the art, often manually performed. Caused by size of the welding torch and the limited penetration depth of multi-pass welding, grove angles of 45° or more are essential. This leads to a high volume weld metal and a high heat input into the base material as well as to a high consumption of filler material. Weld distortion and therefore straightening of the components are cost drivers, too.The paper will be present the latest developments at the Fraunho...

LBW of steel-aluminum corner joints generated by selected laser material melting

Continuously rising demands on automotive and railway structures require significant weight reductions. Therefore lightweight concepts using metallic hybrid constructions, like steel-aluminum structures, are becoming more and more interesting. The required efficient joining technologies, especially for deformable hybrid body structures are not sufficiently applicable up to now. Conventional heat based joining techniques, like welding or brazing, mainly fail because of pronounced intermetallic phase formations in conjunction with reduced ductility. Therefore Fraunhofer IWS developed a new laser based joining technology especially for high deformable hybrid car body applications.For the joining of hybrid T-joints a controlled laser remote process has been combined with a novel construction approach, the so-called “web-slot-design”. In essence, a special contour is laser-cut into two separate sheet metal components (aluminum web plate / steel cover sheet). The T-joint assembly is produced by placing the web ...

Fatigue Behaviour of Laser Beam Welded Circular Weld Seams under Multi-Axial Loading

With modern laser beam sources welding processes can be developed, that allow the joining of otherwise barely realisable material and geometrical constellations such as dissimilar welded, thick-walled shaft-hub joints for powertrain systems. Current design recommendations do not offer solutions to account for the cyclic strength under torsional loading for welded structures. In order to bridge the gap between cost and time consuming prototype testing and laboratory tests of basic homogeneous material samples, a test system combining axial and torsional loading was used. For this purpose application oriented test parts are designed to mimic the weld seam geometry, stiffness and heat dissipation conditions of the real structural part at its best. The dissimilar joints were realised for two material combinations: cast iron GJS-600-3 with case hardened steel 16MnCr5 and 42CrMo4 with 16MnCr5. The latter combination showed only a slightly higher cyclic strength compared to the cast iron/steel combination. A systematic optimization of the laser beam welding process leads to a fatigue behaviour under multi-axial loading conditions, where the cast iron/case hardened steel combination still met the strength specification required.

Prospects of welding foils with solid state laser for lithium-ion batteries

Lithium-ion batteries will become a key element in future electro mobility. In a layered pouch cell design the electrical contacts consist of conductive foil tapes that have to be welded to the terminal. Common used ultra-sonic welding technologies have some process inherent restrictions like risk for mechanical damaging of the 10…20 µm thin Al or Cu foils, wear of the welding-sonotrode and limited mechanical strength and electrical conductivity of the welding spot caused by the adhesive bonding interfaces.For a high volume and high power applications for future electro mobility the laser beam welding technology with high quality (HQ) solid state laser offers new possibilities. Beside the easy laser beam welding (LBW) process automation a higher strength and a lower electrical resistance of the weld caused by a fully metallic bonding can be achieved. But laser beam welding of 10…20 µm thin foil packages is challenging with respect to the gap condition in overlap configuration, necessary new clamping concepts and welding strategies to minimize the heat input. In the paper weld joint geometries, influence of laser sources and beam deflection techniques will be specifically analyzed.Lithium-ion batteries will become a key element in future electro mobility. In a layered pouch cell design the electrical contacts consist of conductive foil tapes that have to be welded to the terminal. Common used ultra-sonic welding technologies have some process inherent restrictions like risk for mechanical damaging of the 10…20 µm thin Al or Cu foils, wear of the welding-sonotrode and limited mechanical strength and electrical conductivity of the welding spot caused by the adhesive bonding interfaces.For a high volume and high power applications for future electro mobility the laser beam welding technology with high quality (HQ) solid state laser offers new possibilities. Beside the easy laser beam welding (LBW) process automation a higher strength and a lower electrical resistance of the weld caused by a fully metallic bonding can be achieved. But laser beam welding of 10…20 µm thin foil packages is challenging with respect to the gap condition in overlap configuration, necessary new clamping conce...

Laser beam welding with high-frequency beam oscillation: Welding of dissimilar materials with brilliant fiber lasers

Brilliant laser beam sources in connection with a high frequent beam oscillation make it now possible to join metallic material combinations, which have been conventionally non-laser weldable up to now. It concerns especially such combinations like Al-Cu, where brittle intermetallic phases occur. Extreme small weld seam with high aspect ratio leads to very short melt pool life time. These allow an extensive reduction of the heat input. On the other side the melting behavior at metallic mixed joint, seam geometry, chemical composition, melt pool turbulence and solidification behavior can be influenced by a high frequent time-, position-and power-controlled laser beam oscillation.Brilliant laser beam sources in connection with a high frequent beam oscillation make it now possible to join metallic material combinations, which have been conventionally non-laser weldable up to now. It concerns especially such combinations like Al-Cu, where brittle intermetallic phases occur. Extreme small weld seam with high aspect ratio leads to very short melt pool life time. These allow an extensive reduction of the heat input. On the other side the melting behavior at metallic mixed joint, seam geometry, chemical composition, melt pool turbulence and solidification behavior can be influenced by a high frequent time-, position-and power-controlled laser beam oscillation.